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| United States Patent |
5,183,198
|
|
Tamehiro
, et al.
|
February 2, 1993
|
Method of producing clad steel plate having good low-temperature
toughness
Abstract
A method of producing clad steel plate comprises the steps of preparing an
assembly slab by superposing a stainless-steel or nickel alloy cladding
material onto base metal consisting essentially of, by weight, 0.020 to
0.06% carbon, 0.5% or less silicon, 1.0 to 1.8% manganese, 0.03% or less
phosphorus, 0.005% or less sulfur, 0.08 to 0.15% niobium, 0.005 to 0.03%
titanium, 0.05% or less aluminum, 0.002 to 0.006% nitrogen, and one or two
elements selected from among a group consisting of 0.05 to 1.0% nickel,
0.05 to 1.0% copper, 0.05 to 0.5% chromium, 0.05 to 0.3% molybdenum and
0.001 to 0.005% calcium, with the balance being iron and unavoidable
impurities, and welding its periphery; heating the slab to 1100.degree. to
1250.degree. C.; rolling the slab at a reduction ratio of 5 or more and a
rolling finish temperature of 900.degree. to 1050.degree. C.; air cooling
for 60 to 200 seconds; cooling the slab from a temperature of at least
750.degree. C. to 555.degree. C. or below at a cooling rate of 5.degree.
to 40.degree. C./sec, and following this by air cooling.
| Inventors:
|
Tamehiro; Hiroshi (Kimitsu, JP);
Ogata; Yoshinori (Kimitsu, JP);
Terada; Yoshio (Kimitsu, JP)
|
| Assignee:
|
Nippon Steel Corporation (Tokyo, JP)
|
| Appl. No.:
|
793959 |
| Filed:
|
November 15, 1991 |
Foreign Application Priority Data
| Current U.S. Class: |
228/186; 148/529; 228/231; 228/262.41; 428/679; 428/683 |
| Intern'l Class: |
B23K 031/02 |
| Field of Search: |
228/231,263.15,191,186,235
420/126,127,128
428/679,683
148/12 E,12 EA
|
References Cited
U.S. Patent Documents
| 4360391 | Nov., 1982 | Yamamura et al. | 148/12.
|
| 4464209 | Aug., 1984 | Taira et al. | 428/683.
|
| 4736884 | Apr., 1988 | Tsuyama et al. | 228/235.
|
| 4755233 | Jul., 1988 | Baralis et al. | 148/12.
|
| 4795078 | Jun., 1988 | Kuroki et al. | 228/131.
|
| 4842816 | Jun., 1989 | Miyasaka et al. | 420/126.
|
| 4908280 | Mar., 1990 | Omura et al. | 428/679.
|
| 4917969 | Apr., 1990 | Pircher et al. | 228/231.
|
| 4960470 | Oct., 1990 | Honkura et al. | 148/12.
|
| Foreign Patent Documents |
| 60-216984 | Oct., 1985 | JP.
| |
| 62-16892 | Jan., 1987 | JP.
| |
| 63-130283 | Jun., 1988 | JP.
| |
Primary Examiner: Seidel; Richard K.
Assistant Examiner: Mah; Chuck Y.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Claims
What is claimed is:
1. A method of producing clad steel plate comprising the steps of obtaining
an assembly slab by superposing a stainless steel cladding material and a
base metal consisting essentially of, by weight,
______________________________________
Carbon 0.020 to 0.06%
Silicon 0.5% or less
Manganese 1.0 to 1.8%
Phosphorus 0.03% or less
Sulfur 0.005% or less
Niobium 0.08 to 0.15%
Titanium 0.005 to 0.03%
Aluminum 0.05% or less
Nitrogen 0.002 to 0.006%
______________________________________
with the balance being iron and unavoidable impurities;
seal-welding the periphery of the assembly slab;
heating the slab to a temperature in the range of 1100.degree. to
1250.degree. C.;
rolling the slab at a reduction ratio of 5 or more;
rolling the slab at a finish temperature of 900.degree. to 1050.degree. C.;
air cooling the slab for 60 to 200 seconds to promote recrystallization of
.gamma. structure;
cooling the slab from a temperature of at least 750.degree. to an arbitrary
temperature of 550.degree. or below at a cooling rate of 5.degree. to
40.degree. C./sec; and
air cooling the slab.
2. The method according to claim 1 wherein the cladding material is a
nickel alloy.
3. The method according to claim 2 wherein the base metal includes one or
two elements selected from the group consisting of, by weight,
______________________________________
Nickel 0.05 to 1.0%
Copper 0.05 to 1.0%
Chromium 0.05 to 0.5%
Molybdenum 0.05 to 0.3%
Calcium 0.001 to 0.005%.
______________________________________
4. The method according to claim 1 wherein the base metal includes one or
two elements selected from the group consisting of, by weight,
______________________________________
Nickel 0.05 to 1.0%
Copper 0.05 to 1.0%
Chromium 0.05 to 0.5%
Molybdenum 0.05 to 0.3%
Calcium 0.001 to 0.005%.
______________________________________
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of producing clad steel plate having
good low-temperature toughness in its as-rolled condition, in which the
cladding material is a stainless steel, nickel alloy or other high alloy
having good corrosion-resistance, and the base metal is a designated low
alloy (low C - Mn - high Nb - trace Ti).
2. Description of the Prior Art
Considerations of safety and economic efficiency are resulting in
increasing use of steel pipe clad with high alloy cladding materials such
as stainless steel and nickel alloy for large-diameter pipelines used for
transporting crude oil and natural gas, which contain a high level of
corrosive substances such as H.sub.2 S, CO.sub.2 and Cl.sup.-.
Conventionally such pipes have been manufactured by UOE forming of rolled
clad steel plate, welding the seam, and reheating and cooling (solution
treatment) of the whole pipe. Recently, however, techniques have been
developed that are aimed at achieving the requisite properties in the
as-rolled condition, i.e. without the use of solution treatment. Such
techniques are disclosed by JP-A60-216984, JP-A62-16892 and JP-A63-130283,
for example.
However, with these methods it is exceedingly difficult to obtain cladding
material that has good corrosion-resistance together with a base metal
that has good tensile strength and low-temperature toughness. The reason
for this is that, while rolling at higher temperatures (at or above
900.degree. C.) improves the corrosion-resistance of the cladding
material, the low-temperature toughness of the base metal is improved by
rolling at a low temperature. As a result, the need to use a lower rolling
temperature in the prior art has meant that the corrosion-resistance of
the clad steel has suffered.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method of producing
high-alloy-clad steel plate in which high corrosion-resistance of the
cladding material is combined with high tensile strength and
low-temperature toughness of the base metal.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a method of producing clad steel plate
comprising the steps of obtaining an assembly slab by superposing a
cladding material consisting of stainless-steel or nickel alloy, and a
base metal consisting essentially of, by weight,
______________________________________
Carbon 0.020 to 0.06%
Silicon 0.5% or less
Manganese 1.0 to 1.8%
Phosphorus 0.03% or less
Sulfur 0.005% or less
Niobium 0.08 to 0.15%
Titanium 0.005 to 0.03%
Aluminum 0.05% or less
Nitrogen 0.002 to 0.006%
______________________________________
and which also contains, if necessary, one or two elements selected from
among a group consisting of, by weight,
______________________________________
Nickel 0.05 to 1.0%
Copper 0.05 to 1.0%
Chromium 0.05 to 0.5%
Molybdenum 0.05 to 0.3%
Calcium 0.001 to 0.005%
______________________________________
with the balance being iron and unavoidable impurities, and seal-welding
its periphery; heating the slab to a temperature in the range 1100.degree.
to 1250.degree. C.; rolling the slab at a reduction ratio of 5 or more and
a rolling finish temperature of 900.degree. to 1050.degree. C.; following
the rolling with air cooling for 60 to 200 seconds; cooling the slab from
a temperature of at least 750.degree. C. to an arbitrary temperature of
550.degree. C. or below at a cooling rate of 5.degree. to 40.degree.
C./sec, and following this by air cooling.
The stainless-steel of this invention is an austenitic, ferritic,
martensitic or duplex steel, and the nickel alloy is a material such as
Incoloy 825 or Inconel 625 that has high corrosion-resistance. The base
metal is a low alloy with the following properties (values parallel to the
rolling direction and at right-angles thereto): a minimum tensile strength
of X52 (API Standard) and low-temperature toughness of 2vE.sub.-30
.gtoreq.10kg f-m, vTrs.ltoreq.-60.degree. C.
Thus, in accordance with the present invention the assembly slab is
prepared by superposing the cladding material on the base metal and
welding the two together around the periphery. As such, it is preferable
to smooth the contact surfaces of base metal and cladding material
beforehand by grinding or the like, then clean the surfaces by degreasing
and use a vacuum pump to ensure the removal of air from between the
surfaces. Alternatively, a sandwich type arrangement may be used
consisting of sandwiching a separating material (such as Al.sub.2 O.sub.3)
between the cladding material of two slabs prepared by the above process,
followed by seal-welding of the periphery.
Details of the present invention will now be explained. The distinguishing
feature of the present invention is that, using a low C - high Nb - trace
Ti base metal, it is possible to obtain a cladding material that is highly
corrosion-resistant while at the same time obtaining a base metal having
high tensile strength and toughness even when finish rolling is performed
at a high temperature. To achieve cladding material having high
corrosion-resistance, alloy elements are dissolved during the reheating,
and high-temperature rolling of the slab is then followed by air cooling
for an appropriate period to promote the recrystallization of the .gamma.
structure, and in addition the precipitation of .sigma. phase (Cr
carbides) and the like has to be suppressed by using quenching.
However, rolling the base metal at the kind of high temperature needed for
this recrystallization results in insufficient refinement of the grain
size and, therefore, lack of sufficient low-temperature toughness. Studies
were therefore carried out to find a base metal composition that would
provide a good balance between tensile strength and toughness even when a
high rolling finish temperature is used. These studies led to the
discovery that the addition of high Nb to low C - trace Ti steel was
effective, and a new method of producing clad steel plate was invented by
applying this to rolled clad steel.
High Nb steel has been reported in Metals Technology, vol. 11 (1984), pages
535 and 545, and in the Niobium Technical Report 8 (1990), but there is no
mention of research relating to its application to high alloy clad steel
plate.
The reheating, rolling and cooling conditions used in the present invention
will now be described. In accordance with this invention the assembly slab
is reheated at a temperature of 1100.degree.-1250.degree. C. It is
necessary to do this to ensure the corrosion-resistance of the cladding
material together with the tensile strength and toughness of the base
metal. The lower limit of 1100.degree. C. is required to ensure sufficient
dissolution to provide the cladding material with good
corrosion-resistance and for the .gamma. structure recrystallization that
follows finish rolling at a temperature of 900.degree. C. or higher.
However, a reheating at over 1250.degree. C. will produce a coarsening of
the austenite (.gamma.) grains, and of the grain size after rolling,
degrading the low-temperature toughness of the base metal.
The reheated slab has to be rolled at a finish temperature of
900.degree.-1050.degree. C. and a reduction ratio in the range of 5 to 12,
more preferably in the range of 6 to 12. The lower limit of 5 is specified
(1) to ensure that there is perfect metallurgical bonding between cladding
material and base metal and (2) to refine the grain size of the base
metal. Perfect metallurgical bonding between cladding material and base
metal is required to ensure the service performance of the cladding
material, and a higher reduction ratio results in a better performance.
The minimum reduction ratio depends on the reheating temperature and on
rolling temperature; in the case of the present invention in which a high
rolling temperature is used, the minimum reduction ratio is 5.
In accordance with this invention, rolling is finished at
900.degree.-1050.degree. C. If the rolling is finished at a temperature
below 900.degree. C., recrystallization of the .gamma. structure of the
cladding material will not take place, resulting in a marked deterioration
in the corrosion-resistance (for example pitting corrosion-resistance
measured after immersion for 48 hours in a 10% solution of FeCl.sub.3
.multidot.6H.sub.2 O). With respect to corrosion-resistance, the higher
the rolling finish temperature the better. However, too high a temperature
can result in a degradation of the low-temperature toughness by preventing
refinement of the crystal grains of the base metal, hence a maximum
rolling finish temperature of 1050.degree. C. has been specified.
In further accordance with this invention, after the rolling is finished
the slab is air cooled for 60 to 200 seconds, cooled from a temperature of
at least 750.degree. C. to an arbitrary temperature of 550.degree. C. or
below at a cooling rate of 5.degree. to 40.degree. C./sec, and this is
followed by air cooling to the ambient temperature. The air cooling
following the rolling is to promote the recrystallization of the .gamma.
structure and enhance the corrosion-resistance. Good corrosion-resistance
will not be obtained if instead of this air cooling the slab is directly
quenched after being rolled. This air cooling has to last at least 60
seconds. On the other hand, too long an air cooling period can allow the
temperature of the clad steel to drop, precipitating .sigma. phase (Cr
carbides) and degrading the corrosion resistance of the cladding material.
Thus, while it depends on the thickness of the steel, an upper limit of
200 seconds has been specified for the air cooling period, and it is also
necessary to apply water cooling from a temperature of at least
750.degree. C. It is necessary to cool the steel to 550.degree. C. or
below at a cooling rate of 5.degree. to 40.degree. C./sec so that (1) the
precipitation of .sigma. phase (Cr carbides) is suppressed and (2) the
base metal is toughened by the accelerated cooling. After cooling the
steel to below a prescribed temperature, it is air cooled. Moreover,
reheating (tempering) the clad steel at a temperature below the
transformation point Ac.sub.1 to improve the low-temperature toughness and
for dehydrogenation and other such purposes has no adverse effect on the
distinguishing features of the invention.
The reasons for the specified limitations on the alloying elements of the
base metal will now be explained.
To ensure the tensile strength and low-temperature toughness of the base
metal as well as the corrosion-resistance of the cladding material, the
invention specifies the chemical composition of 0.020 to 0.06% C, 1.0 to
1.8% Mn, 0.08 to 0.15% Nb and 0.005 to 0.03% Ti.
In the case of C and Mn, the lower limits are the minimum amounts that have
to be added for the Nb to bring out the precipitation hardening and grain
size refinement effects of these elements to ensure the strength and
toughness of the base metal and welded portions. The specified maximum
amounts are the upper limits that have to be observed in order to produce
a base metal with good low-temperature toughness and field weldability. If
the C content is too high, carbon will diffuse into the cladding material
when the assembly slab is reheated, reducing the corrosion resistance.
Therefore, specifying an upper limit of 0.06% for the carbon content of
the base metal is also done to ensure the corrosion-resistance of the
cladding material.
Niobium and titanium are essential elements in this invention, in the
amounts of 0.08 to 0.15% for niobium and 0.005 to 0.03% for titanium. In
controlled rolling, niobium contributes to grain refinement and
precipitation hardening, thereby strengthening and toughening the steel.
For the purposes of this invention which specifies a high rolling
finishing temperature of at least 900.degree. C., the addition of at least
0.08% Nb is required. This promotes grain refinement and precipitation
hardening, resulting in clad steel with a higher tensile strength and
toughness than clad steel produced by the conventional method. An upper
limit of 0.15% Nb is specified because a higher level will reduce the
weldability and the toughness of the welded portions.
By forming fine-grained TiN and suppressing the coarsening of .gamma.
grains at welded portions and during the reheating of the slab, titanium
enhances the toughness of the base metal and of weld heat-affected zones.
This is particularly important for the steel of this invention which is
finish rolled at a high temperature. For the TiN to be fully effective at
least 0.005% Ti is required. As excessive titanium will produce coarsening
of the TiN and give rise to precipitation hardening caused by TiC, thereby
degrading the low-temperature toughness, 0.03% has been specified as the
upper limit.
The reasons for the specified limitations on the other elements will now be
explained.
Silicon increases the strength and toughness of steel, but too much silicon
can reduce weldability and the toughness of the heat-affected zones, hence
an upper limit of 0.5% has been specified. As titanium has a sufficient
deoxidization effect, the addition of silicon is not essential.
The impurities phosphorus and sulfur are limited to 0.03% and 0.005%
respectively with the aim of further improving the low-temperature
toughness of the base metal and welded portions. Reducing the P content
prevents intergranular fracture, while low S prevents the toughness being
impaired by MnS. Preferably, phosphorus should be controlled to 0.01% or
less and sulfur to 0.003% or less.
Aluminum is usually included in steel as a deoxidization agent, but as
titanium or silicon can also be used for this, aluminum is not an
essential element. An upper limit of 0.05% Al is specified, as a higher
aluminum content causes an increase in the amount of aluminate inclusions,
impairing the cleanness of the steel.
Nitrogen improves the toughness of the base metal and heat-affected zones
by forming TiN, which suppresses the coarsening of .gamma. grains. For
this, at least 0.002% is required. Too much nitrogen can produce surface
defects, and in the form of solid-solution nitrogen, can impair the
toughness of heat-affected zones, so it is necessary to limit the maximum
nitrogen content to 0.006%.
The reasons for adding nickel copper, chromium, molybdenum and calcium will
now be explained.
The main object of adding these elements to the base chemical composition
is to improve the tensile strength, toughness and other properties of the
base metal without adversely affecting the superior qualities of the
inventive steel. As such, these elements have their own limits.
Nickel improves the strength and toughness of the steel without any adverse
effect on weldability or on the toughness of heat-affected zones. When the
copper is also added, nickel has the additional effect of preventing
hot-cracking during plate rolling. The limit of 1.0% is based on cost
considerations. Copper improves corrosion resistance and resistance
against hydrogen-induced cracking, but in amounts over the specified limit
of 1.0% can impede production by causing hot-cracking during plate
rolling. Chromium and molybdenum both improve the strength of the steel,
but in excessive amounts impair weldability and the toughness of
heat-affected zones. Therefore an upper limit of 0.5% has been specified
for chromium and 0.3% for molybdenum. The lower limit of 0.05% for nickel,
copper, chromium and molybdenum is the minimum amount required for the
element to exhibit its effect.
Calcium controls the shape of sulfides (MnS) and improves low-temperature
toughness (such as Charpy test values), and also is highly effective for
improving resistance to hydrogen-induced cracking. At least 0.001% Ca is
required to obtain these effects, but adding more than 0.005% will give
rise to large amounts of CaO and CaS, causing the formation of large
inclusions, impairing the cleanness of the steel as well as the toughness
and weldability. An effective way of improving resistance to
hydrogen-induced cracking is to reduce the sulfur and oxygen contents to
not more than 0.001% and 0.002% respectively.
The present invention makes it possible to produce high quality clad steel
for pipe and other applications in which the base metal has high tensile
strength and low-temperature toughness combined with highly
corrosion-resistant cladding material, and there is no need to subject the
entire pipe to solution treatment. The method of this invention can
therefore be used to save energy and reduce the amount of work operations.
In addition, it provides a marked improvement in pipeline safety. While a
heavy plate mill is the preferred application for the method of the
invention, it can also be applied to the production of hot coil. The
excellent low-temperature toughness and weldability of steel produced by
this method makes it particularly suitable for cold-region pipelines.
EXAMPLES
Continuous casting was used to manufacture base metal steel slabs. These
slabs were of various compositions and had a thickness of 240 mm. The
slabs were then rolled to a prescribed thickness and one surface of each
slab was mechanically smoothed and overlaid by cladding material
consisting of various thicknesses of stainless steel (SUS 316L) or Incoloy
825 to form an assembly slab which was then seal-welded around its
periphery. For this, the cladding material had been rolled to a thickness
of 3 mm.
Sandwich type assembly slabs were further prepared by sandwiching a
separating material between two slabs of cladding material prepared as
described above, and the periphery was then welded. The full area of the
contact surfaces was smoothed, cleaned, degreased, and a vacuum pump was
used to remove any air between the contact surfaces.
These sandwich assembly slabs were then subjected to reheating, rolling and
cooling steps under various conditions to produce clad steel materials.
This was followed by an investigation of base metal tensile strength and
low-temperature toughness (using the Charpy impact test), the
corrosion-resistance of the cladding material (through evaluation of the
presence or absence of pitting corrosion after immersion in a 10% solution
FeCl.sub.3 .multidot.6H.sub.2 O for 48 hours at 15.degree. C. in the case
of SUS 316L and 30.degree. C. in the case of Incoloy 825), and the bonding
between base metal and cladding material (by ultrasonic probe). Details of
conditions, compositions, and results are listed in Table 1.
The base metal and cladding material of the clad steels produced by the
method of the present invention (Specimens No. 1 to 10) exhibited good
properties. In contrast, the base metal or the cladding material of the
comparative steels not produced by the method of the present invention
(Specimens No. 11 to 26) exhibited inferior properties.
High carbon and low manganese in the case of No. 11, and insufficient
niobium in the case of No. 12, resulted in poor low-temperature toughness.
The poor low-temperature toughness of No. 13 was caused by the absence of
titanium, while in the case of No. 14 the cause was low nitrogen. The poor
low-temperature toughness of No. 15 was caused by too much nitrogen. In
the case of No. 16, excessive silicon and manganese resulted in good
tensile strength but poor low-temperature toughness. The poor strength,
corrosion-resistance and bonding between base metal and cladding material
of No. 17 were the result of reheating at too low a temperature, while in
the case of No. 18 the low-temperature toughness was degraded by a
reheating temperature that was too high. A low rolling finishing
temperature degraded the corrosion-resistance of No. 19, while a rolling
finishing temperature that was too high was the cause of the poor
low-temperature toughness exhibited by No. 20. In the case of No. 21, the
poor corrosion-resistance shows the adverse effect of using an air-cooling
period that was too short. The poor strength and corrosion-resistance of
No. 22, on the other hand, were caused by an overlong period of air
cooling that delayed the start of the water cooling. An excessively low
cooling rate was the cause of the poor strength and corrosion-resistance
of No. 23, while the poor low-temperature toughness of No. 24 was caused
by a cooling rate that was too high. In the case of No. 25, the low
reduction ratio resulted in insufficient adhesion between cladding
material and base metal. The strength and corrosion-resistance of No. 26
were degraded by stopping the water cooling at too high a temperature.
TABLE 1
__________________________________________________________________________
Chemical composition (wt %, *ppm)
No.
C Si Mn P S Nb Ti Al *N other
__________________________________________________________________________
Inventive
1 0.032 0.23
1.51 0.008
0.001 0.098
0.009 0.024
34
steels 2 0.034 0.28
1.42 0.012
0.002 0.143
0.020 0.018
54
3 0.051 0.08
1.24 0.003
0.003 0.105
0.012 0.002
23
4 0.023 0.23
1.75 0.007
0.001 0.110
0.016 0.043
35
5 0.040 0.35
1.55 0.005
0.006 0.092
0.018 0.011
23
6 0.018 0.25
1.56 0.003
0.002 0.084
0.007 0.033
25
7 0.033 0.24
1.49 0.020
0.002 0.103
0.015 0.023
37 0.35 Ni
8 0.025 0.12
1.38 0.013
0.001 0.120
0.013 0.015
28 0.12 Mo, 0.0035 Ca
9 0.031 0.23
1.25 0.004
0.001 0.105
0.013 0.014
22 0.21 Cr, 0.0023 Ca
10 0.029 0.33
1.58 0.012
0.002 0.092
0.008 0.010
36 0.25 Ni, 0.28 Cu
Comparative
11 0.081 0.18
0.98 0.005
0.001 0.105
0.016 0.027
33
steels 12 0.023 0.28
1.57 0.003
0.002 0.070
0.018 0.021
35 0.23 Ni
13 0.035 0.23
1.42 0.015
0.002 0.098
-- 0.017
26
14 0.032 0.25
1.62 0.009
0.001 0.105
0.011 0.027
16
15 0.033 0.18
1.54 0.008
0.002 0.104
0.018 0.021
62
16 0.034 0.57
1.89 0.006
0.001 0.120
0.016 0.018
23
17 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
18 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
19 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
20 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
21 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
22 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
23 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
24 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
25 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
26 0.032 0.28
1.54 0.008
0.002 0.105
0.012 0.023
38
__________________________________________________________________________
Production conditions
Reheating Finishing
Air Water cooling
Water cool-
Steel thick-
temper-
Reduc-
rolling
cooling
starting
Cooling
ing stopping
ness
Remarks
ature tion
temperature
period
temperature
rate temperature
separation)
(cladding
No.
(.degree.C.)
ratio
(.degree.C.)
(sec)
(.degree.C.)
(.degree.C./sec)
(.degree.C.)
(mm) material)
__________________________________________________________________________
Inventive
1 1150 8.0 960 120 880 12 480 25 Incoloy 825
Steels 2 1150 10.0
1020 80 920 22 500 20 Incoloy 825
3 1200 11.8
940 120 790 32 520 17 Incoloy 825
4 1120 6.7 910 145 860 9 370 30 Incoloy 825
5 1150 10.0
1000 160 780 16 420 20 Incoloy 825
6 1150 10.0
930 70 850 30 Room 20 Incoloy 825
temperature
7 1150 8.0 920 160 760 18 430 25 Incoloy 825
8 1100 5.6 920 120 840 7 450 36 Incoloy 825
9 1200 13.3
1030 70 870 34 530 15 SUS 316 L
10 1150 9.1 970 100 860 19 410 22 Incoloy 825
Comparative
11 1150 10.0
950 110 860 23 480 20 SUS 316 L
Steels 12 1150 10.0
930 90 840 18 430 20 Incoloy 825
13 1150 10.0
920 120 800 26 440 20 Incoloy 825
14 1150 10.0
960 100 830 20 470 20 Incoloy 825
15 1150 8.0 990 120 870 14 460 25 Incoloy 825
16 1150 8.0 940 80 870 17 420 25 Incoloy 825
17 1000 8.0 950 110 830 19 370 25 Incoloy 825
18 1280 10.0
980 90 870 25 420 20 Incoloy 825
19 1150 10.0
870 120 790 20 500 20 Incoloy 825
20 1150 10.0
1060 90 920 22 480 20 Incoloy 825
21 1150 10.0
940 45 870 21 440 20 Incoloy 825
22 1150 10.0
960 210 730 18 500 20 Incoloy 825
23 1150 8.0 930 80 820 3 460 25 Incoloy 825
24 1150 8.0 940 80 820 46 430 25 Incoloy 825
25 1150 4.5 980 100 880 21 480 25 Incoloy 825
26 1200 8.0 980 100 870 20 580 25 Incoloy 825
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Bonding of
cladding material
Corrosion-resistance
of
Properties of base metal Defects detected
cladding material
No.
YS (kgf/mm.sup.2)
TS (kgf/mm.sup.2)
vE.sub.-30 (kgf-m)
vTrs (.degree.C.)
by ultrasonic Probe
Corrosion
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resistance
Inventive
1 48.2 59.7 32.2 -76 No No
Steels 2 50.3 60.3 25.6 -80 No No
3 49.3 58.8 23.6 -83 No No
4 49.2 59.2 35.6 -74 No No
5 52.0 61.3 22.9 -74 No No
6 50.2 63.1 23.4 -76 No No
7 47.0 58.1 27.6 -80 No No
8 48.3 57.5 38.2 -70 No No
9 49.0 60.3 25.6 -82 No No
10 51.2 62.3 29.0 -78 No No
Comparative
11 47.8 57.8 28.3 -46 No Yes
Steels 12 50.3 59.4 26.4 -57 No No
13 48.9 58.9 26.9 -52 No No
14 51.2 60.9 32.8 -56 No No
15 48.8 58.9 26.8 -54 No No
16 48.9 63.2 12.3 -37 No No
17 38.6 50.5 30.6 -80 Yes Yes
18 52.0 61.3 10.1 -35 No No
19 49.8 59.9 26.7 -78 No Yes
20 50.8 60.6 25.7 -46 No No
21 49.2 60.5 26.9 -68 No Yes
22 46.3 54.4 28.8 -64 No Yes
23 41.9 51.0 30.2 -73 No Yes
24 48.5 65.1 18.7 -28 No No
25 49.0 58.9 8.9 -32 Yes No
26 45.2 54.3 26.7 -75 No Yes
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